> If smallpox-as-a-bioweapon is even a slight possibility why don’t we start vaccinating for it again?

Well this would not treat the problem, because smallpox is not the problem here. The fact that we're squishy fragile hosts/food, and bioweapons are getting easier and easier to make, is the problem.

If there was a smallpox vaccination campaign, unless completely secret, the bad actors would simply move on to a different virus/variant/fungus/bacteria.

The only real protection against any of this is to make sure the world has a similar vaccination regime, to ensure mutual destruction.